Basic_Electrical_Wiring

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					Basic Electrical Wiring

  Agricultural Science and
        Technology
                   Electrical Safety
                     "Shocking Statistics“

 There are approximately 290 accidental electrocutions each year.

 An additional 800 people die in fires caused by faulty electrical
    systems every year.

 Thousands are shocked and burned as the result of accidental
    contact with electricity every year.

    An estimated $1.2 billion in property damage occurs each year due
    to faulty use of electricity.
                 Electricity
 Electricity is the flow of electrons in a
  conductor.

 The electrons must have a path to and
  from its source.

 This path is called a circuit.
                Electricity
 Various electrical devices are used as a
 part of the circuit.

 These devices are used for a variety of
 activities, such as turning the electricity off
 and on, providing electricity to various
 lights or appliances, etc.
   Types of Electrical Currents
 Electrical current comes in two forms:
  – Direct current (DC)
      Flows in only one direction.
      It is usually generated by battery-base electrical
      systems and used in the electrical systems of
      internal combustion engines or flashlight batteries.
  – Alternating current (AC)
      Reverses the direction of flow of current many
      times each second.
      AC is the type used in homes, factories, etc.
          Electrical Service
 Service is provided to homes, businesses
 and other small users of electricity by
 three wires from a utility pole.

 Two of the wires are “hot,” each carrying
 120 volts.

 The other wire is “neutral,” and provides
 the return path for electricity.
     Electrical Service (cont.)
 These wires are connected to a service
 entrance, which is where the electricity
 enters a building.

 A meter is used in the service entrance to
 measure the amount of electricity being
 used.
     Electrical Service (cont.)
 The service entrance is grounded with a
  wire connected to a ground rod driven
  several feet into the ground.

 It is needed to provide a return path to the
  ground and to carry away stray electrical
  current out of the system.
               Service Panel
 Follows the meter.


 It houses the circuit
  breakers for the
  system and is used to
  distribute the power to
  individual circuits
  throughout the
  system.
                Overcurrent
 When a circuit uses too much electricity, an
  overcurrent causes a circuit breaker to trip,
  shutting down the power to that circuit.

 The excessive heat caused by an overcurrent
  condition may burn or damage a conductor’s
  insulation and cause a fire.

 A circuit breaker is a heat-sensitive switch,
  which automatically trips when electricity
  demand is too great which causes the
  temperature in the conductor to get too hot.
         Amps Volts Watts
    The following relationship exists
    between Amps, Volts and Watts.
 Amperes are a measure of the rate of flow
 of electricity in a conductor.

 Volts are a measure of electrical pressure.

 Watts are a measure of the amount of
 energy or work that can be done by
 amperes and volts.
 Amps Volts Watts (cont.)

Thus, the following relationship exists.

       Work = Pressure x Flow
                Or
       Watts = Volts x Amperes
    Amps Volts Watts (cont.)
 This formula is commonly referred to as
 the West Virginia Formula

                    W=VA

 When we know any two variables of the
 formula, we can calculate the other.
Amps Volts Watts (cont.)

         Formulas
    Watts = Volts x Amps
    Volts = Watts / Amps
    Amps = Watts / Volts
       Calculating Amperage

If we have a 100 watt lamp plugged into a 120 volt
receptacle, we can determine the rate of flow or the
              amperes for that circuit.
        Amps = 100 Watts / 120 Volts
             100 / 120 =.833 Amps
           Calculating Watts

If a water heater operates at 20 amps on a 240 volt
    circuit, what is the wattage of the appliance?
        Watts = 240 Volts x 20 Amps
          4800 Watts =240V x 20A
                  Watts=4800
            Calculating Volts
If an electric motor operates at 2880 watts and 12
amps, what would be the voltage requirement for
                    that motor?
       Volts = 2880 Watts / 12 Amps
            2880 / 12 = 240 Volts
 Identify and draw various symbols
 used in drawing wiring diagrams or
             schematics.


What symbols are used in drawing various
electrical devices?

In order to successfully draw a wiring circuit
on paper, one needs to use various symbols
that represent the equipment.
Cable Types
       Cable Types (cont.)
In cable, there are four different colors or
kinds of wire that one will use depending
on the type of wire that is being used.
Using 12-gauge wire as the example,
there are four types of cable that one may
buy.
      Cable Types (cont.)

One is 12/2 with ground, which has one
black conductor, one white conductor, and
a bare ground conductor.
      Cable Types (cont.)
A second cable is 12/2 without ground,
which is the same as 12/2 with ground
except that no bare ground conductor
exists.
      Cable Types (cont.)
A third type of cable is 12/3 with ground,
which has one black conductor, one white
conductor, one red conductor, and one
bare ground conductor.
       Cable Types (cont.)
The last type is 12/3 without ground which
is like the 12/2 without ground. It has the
three colored conductors, but no bare
conductor.
The symbols used for conductors
  and their respective colors are:
              Symbols
Various devices are used as lamp holders,
       switches, and receptacles.
Symbols (cont.)
Symbols (cont.)
Symbols (cont.)
 Additional symbols are used
   to identify terminals and
indicate if wires are spliced or
       just crossing over.
Symbols (cont.)
Symbols (cont.)
            Diagramming

 Generally, black and red conductors
 carry “hot” power or current from the
 source to the devices within the
 circuit.

 The white conductor is always used to
 carry the current back to the source.
        Diagramming (cont.)
 When completing the diagram, it may be
 helpful to draw the white, neutral
 conductor from the source to its final
 destination within the circuit, first.

 Duplex receptacles and pull-chain lamp
 holders are normally wired so that they
 have “hot” or un-switched power at all
 times.
  Diagramming-3 way switches
 3-way switches are always used in pairs.


 They are needed when one wishes to
 control a light from two different locations.
     Diagramming-3 way switches
              (cont.)
 3-way switches have
  three screws or terminals,
  one is called control or
  common terminal.

 It is often darker colored
  than the other two
  terminals.

 The other two terminals
  are called traveler
  terminals.
    Diagramming-3 way switches
             (cont.)

 When the toggle switch is in one position,
 the common terminal carries current to
 one traveler terminal.

 When the toggle switch is in the other
 position, the common terminal carries
 current to the other traveler terminal.
    Diagramming-3 way switches
             (cont.)

 When diagramming and wiring 3-way switches,
  the hot current always enters the control terminal
  of one of the switches and always exits out of
  the control terminal of the other switch.

 The traveler terminals from one of the switches
  must connect to the traveler terminals of the
  other switch with no interference.
Diagramming a Single Pole Switch
Circuit
SEP
Breaker




          W ire Nut
Circuit
SEP
Breaker




          12-2 w/g 




                       12-2 w/g 
Diagramming a Three Way Switch
 Circuit
SEP
 Breaker




           W
 Circuit
SEP
 Breaker




           B


               W
 Circuit
SEP
 Breaker




12-2 w/g       12-2 w/g 


                              W




                 12-3 w/g 
            R
 Circuit
SEP
 Breaker
 Circuit
SEP
 Breaker



           B

               W




                   B
 Circuit
SEP
 Breaker




           12-2 w/g
                                 B

                                            W
                           12-2 w/g 



                                                B




                               12-3 w/g 
                       R

				
DOCUMENT INFO
Description: Electrical wiring instruction document. How to manage Electricity? How to plan a house wiring, safety instructions for Electrical system